John Albert Gardner III appears during a brief court hearing in San Diego where his attorney entered pleas of not guilty on his behalf, Wednesday, March 3, 2010. Gardner, 30-year-old sex offender was charged with murdering 17-year-old Chelsea King, who vanished after heading off for a run in a park. Prosecutors say Gardner also faces a special allegation of rape or attempted rape, and a count of assault with intent to commit rape.

The convicted sex offender accused of raping and murdering California high school senior Chelsea King and burying her body in a shallow grave pleaded not guilty to both counts at an arraignment today in San Diego.

John Albert Gardner III was arrested on Sunday, two days before the body of King, 17, was found 10 feet from Lake Hodges in the park where she went missing on Feb. 25 during an afternoon run.

Amid heightened security around the court house, Gardner was flanked by two court officers. His head was shaved and his hands were manacled around the waist of his blue prison jumpsuit.

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Freed To Kill?

Keeping his eyes down, Gardner, 30, simply answered "yes," to a question by the judge whether he understood the charges.

The brief arraignment lasted just a few minutes. No bail was set and the prosecutor did not mention any of the details of the alleged crime. Gardner was assigned a public defender for the arraignment, but that lawyer may not represent him at trial.

Prosecutors said the severity of the accusations, including a "special allegation" that a murder was committed during a rape, could carry the death penalty. The decision to seek capital punishment, however, is weeks away.

"The special allegation does make the defendant eligible for the death penalty," Deputy District Attorney Kristen Spieler said at a press conference following the arraignment. "That decision is made by the D.A., typically after the preliminary hearing and before a trial."

If the district attorney does not seek the death penalty, the charges carry a penalty of 25 years to life.

Gardner's prior record as a convicted sex offender, prosecutors said, would be presented at trial.

Gardner was arrested Monday on suspicion of murder and rape after police found his DNA on an article of clothing that belonged to King.

King's disappearance sparked a 5-day search, in which local, state and federal authorities joined hundreds of volunteers to comb the marshy park looking for the girl or her body.

Former FBI agent and ABC News consultant Brad Garrett said the location of the body likely means King was attacked shortly after she started her jog.

"This was probably a blitz attack. where he sees her jogging and attacks her," he said, adding that it's not uncommon for murderers to leave their victims near the site of the crime.

Gardner, a registered sex offender, pleaded guilty in 2000 to charges of committing lewd and lascivious acts on 13-year-old girl in his parents' home. He served five years of a six-year sentence and was on parole until 2008.

Court psychiatrist, Dr. Matthew Carroll, who evaluated Gardner, pushed for the maximum sentence, as many as 30 years, and said Gardner "would be a continued danger to underage girls in the community."

Dr. Alex Kalish, a colleague, said Carroll was angry that his recommendations were ignored a decade ago.

"Dr. Carroll told the court that [Gardner] showed no insight and expressed no responsibility and that he is a danger. You can't make a stronger statement than that," said Kalish. "The guy is a violent and a predator who shows no remorse.

"There was no effort to consider his report. Apparently the D.A. did what was expedient to get a conviction. It is frustrating that no one considered the psychiatric input. Why ask for it, if you don't consider it," Kalish said.

King's parents joined hundreds of people at a vigil Tuesday night in their daughter's honor to thank the tight-knit community that spent nearly a week trying to bring her home.

"One of the nicknames I always used to call my daughter is my angel, and she'll be my angel forever," said her father, Brent King.

Neighbors in Lake Elsinore, Calif., were outraged to learn Gardner had registered in their town as a sex offender and was living with his mother just yards away from an elementary school.

Police say he might also be connected to the disappearance of Amber DuBois, a 14-year-old who disappeared near San Diego on her way to school in February 2009.

"We've spoke to law enforcement. They are working on Amber's case hand-in-hand with the crime scene for this," DuBois' father, Maurice DuBois, said at a press conference following the arraignment.

"The similarities, the accessibility the location ... there are enough similarities," to make the family suspect Gardner was responsible for his daughter's disappearance, too, DuBois said.

Authorities Monday also linked Gardner to an attack on 23-year-old Candice Moncayo, who identified Gardner from a mug shot as the man who attacked her in December along the same running path where King disappeared.

Moncayo was able to fend off her attacker by elbowing him in the face and running away.